A long term failure rate of about 5% to lateral internal sphincterotomy has been leading to a continuous research for a 
new modalities for treatment of chronic anal fissure. The present study was conducted on 100 patients divided into two 
groups. Group I comprised 50 patients for whom lateral internal sphincterotomy was done. Group II comprised 50 patients who were treated by topical application of nitroglycerine ointment 0.2% twice daily for 6-8 weeks. Anal manometric study for all patients revealed that, maximum resting pressure decreased from a mean value of 98 cm H2O preoperatively to 72 cm H2O one week after the operation in group I and decreased from a mean value of 102 cm H2O before treatment to 76 cm H2O after one week of topical glyceryl trinitrate in group II. Pain relief occurred in 80% during the passage of the first motion, 90% had their pain relief in 2 weeks, 95% in 3 weeks and all patients had their discomfort subsided over 4 weeks in group I, while in group II, 85% reported no pain after 2 weeks, 90% after 4 weeks while pain relief was not obtained in 10%. Complete healing was not achieved in any of the patients of both groups after one week, after 2 weeks , 55% in group I and 35% in group II showed complete healing , at the third week 85% in group I and 75% in group II and at the fourth week all patients in group I and 90% in group II showed complete healing . In group I, temporary incontinence to flatus occurred in 5% whom became completely normal in 3 months, recurrence occurred in 3% within 6 months of surgery. In group II, headache occurred in 15%, hypotension in 5% and recurrence within 6 months of stopping treatment in 15%. In conclusion , internal sphincterotomy with fissurectomy was found to be superior to topical nitroglycerine ointment in the treatment of chronic anal fissure.